for this. I first thought I could beat \Balloon_engraver into
doing what
you need, but there's scant information on it, and I don't know
how to

change the size of the box it creates.

Then I thought I could just use markup and extra-offset to move
the box

where it needed to be, but again, I lack the understanding of how
extra-offset works to be able to use it.

Perhaps, however, with those two suggestion you, or someone else
may be

able to get the results you need.

James,

thanks for reply. I am unexperienced with scheme functions. But I'm
curious too. Could you send me your function allowing me to see,
how it could be done?

Helge

I think you've misunderstood me. I don't know how to get the results
you want. I spent maybe 5 minutes total with \Balloon_engraver and
trying to use #'extra-offset to move a markup box around the note,
but I failed at both. To be fair, I've never used either, and I'm
fairly confident that markup with #'extra-offset could get the result
that you need.

That is to say, I have no functioning solution to your problem, and I
only mentioned this in the hope that it would give you, or someone
else, a starting point.